Improving reception in urban environment
I have a reception question for the many, more experienced folks out there on the board.
Background:
I am running a kiwi (BB-Green) with LZ1AQ dual-loop system. This is set up so that I can switch between the 2 loops, or to sum them together (my usual default mode). Using the recommended
The loops are 1m and oriented as N-S and W-E (True North settings).
I have this set up in my attic of a 2-storey house in an urban area, and generally it works well.
However, one of the neighbours about 15m away (east) has a solar array on their roof. The neighbour west of me, in evenings uses some of those nice bright LED yard lights until about 2300 local time.
Naturally I get a high noise floor from both of these sources. The only relief comes in the time period from about 2300 until local sunrise when both sources are off.
Typically in daytime and evening I get SNR values of ALL between 14 and 20, HF of 10 to 17. Which does not seem to be terrible for an urban location, and most signals are audible, but it's the noise floor that gives grief.
To date:
Tried using different antennas as switched on the AAA antenna system. This works if the loop is the W-E which mostly nulls out the noise sources. As I mostly use the kiwi for MW DXing, this somewhat limits things. HF reception in daytime is not as seriously affected of course.
Using ferrites as suggested in the kiwi forum on all the power supply leads, Ethernet cable, and the antenna input. The kiwi lives near a desktop computer that runs a group of SDRPlay and Airspy USB receivers, all these have ferrites on their USB cables.
Tried isolator transformers (Palomar CM noise filters, 100k-30MHz model), minimal improvement.
Tried connecting radio and computer grounds to earth ground, again minimal improvement.
Tried moving kiwi closer to antenna system so that the balanced connection between control box and antenna is less than 1m ... minimal improvement.
Not sure where to go with this next, what to try next, or if it's gone as far as I can take it in this situation. Any advice welcomed.
Comments
Add to backgrtound:
Using recommended power supply, this system was purchased from SEEED.
As noted I have a ferrite on the PS lead going to the kiwi, just a few inches back from where the barrel connector goes to the BB.
are your neighbors ameniable to adding something to their radiating systems?
I haven't brought this up with them as I would like to go through all the things I might be able to do first, on my gear.
You have done more than what should be necessary on your end. Anything more will no doubt yield negligible improvements.
It is time to attack the SOURCE of the problem. Solar arrays are a common trouble spot. Many are installed poorly and use poor-quality inverters.
Good morning,
I completely understand your difficulties. The modern city is no longer silent, in a radio-electric aspect. Too many sources of domestic interference (lamps LED or Neon, power supply, electrical appliances, inverters, etc.).
The only way would be to mount the antenna considerably higher: 10, 15 or 20 meters above the roofs; a large mast is necessary.
The magnetic loop is an antenna that picks up a lot of magnetic interference coming from the ground. Perhaps choose a horizontal radiating device, less sensitive to these parasites.
My Kiwi SDR (AutreRadioAutreCulture in Trémolat) is installed in a building which also has many sources of interference (15kW and 3kW solar inverters, 2 x 6 kW regulation inverters, office inverters, computer servers, etc.). This is an audiovisual production company.
I solved the parasite problem in two ways :
All this is not easy to achieve in an urban environment.
Originally I wanted to install my Kiwi SDR in the center of Paris, but I gave up because it was necessary to raise the reception antenna too much and this was not authorized by the Paris city hall. So I carried out the installation in Trémolat in Dordogne (France). some photos here :
Best regard, Philippe
I guess you are limited to constructions in the attic of your house. If you have the possibility of mounting a loop horizontally on a mast at a height of 6-10 meters you might get better reduction of those noise sources.
I have used a horizontal "crossed parralel loop" aka Alford loop with good results and nearby noise reduction on HF. For MW reception where the arriving signals are mainly vertically polarized this may not be the best solution but at a minimum you could perhaps try turning your existing loop (or a temporary version) horizontal and see if it helps.
Best regards, Ben
If you have the opportunity to buy it, I recommend the MLA-30 antenna (just don't buy the worthless MLA-30+), which works well in my district polluted with switching power supplies. Additionally, a 12-14 m glass fiber rod, a steel auger to be screwed into the ground as the base of this mast, the antenna is mounted on the rod more than 10 m from the ground, attach the rod to a tree or fence with cable ties, an additional 3-4 m grounding rod is inserted into the ground next to the antenna. You ground the antenna screen at the bottom of the mast and use a thin cable, e.g. rg-174, to bring the signal to the house. Replace the original BIAS-T antenna powered by USB 5V with another one powered by 12-15V and connect it to a transformer power supply, e.g. from a CB radio, the antenna has a trimmer to adjust the gain, such an antenna works perfectly in the range of 60-70% power.
Hi Artur,
The original poster has already got an LZ1AQ loop setup, which is likely to be considerably better than the MLA-30, which IMHO is pretty badly designed and not really up to the task.
I have reverse engineered a MLA-30, and also made extensive comparisons against several other broadband loop designs, so I'm familiar with the performance of most common commercial models.
Unfortunately beyond a certain point, you can only do so much to mitigate interference that is being generated from outside of your property and personal control, especially in an urban area, where the local noise floor can easily be 10 or 20dB worse than somewhere out in the open countryside.
The best solution is to try and find a quiet rural location, where you can remotely site your KiWi and antennas, well away from other noise sources, but I accept that this is not a realistic proposition for most folks.
Regards,
Martin
WRT "LZ1AQ dual-loop system. This is set up so that I can switch between the 2 loops, or to sum them together (my usual default mode).
<snipped>
I have this set up in my attic of a 2-storey house in an urban area, and generally it works well."
If at all possible try and get the loops outside away from property.
I have a loft mounted antenna and it is about 20dB worse in terms of noise than a similar antenna mounted at the bottom of the garden. When loft mounted there is simply too much interaction and close coupling with piping, wiring and other household sources of electrical pollution.
Broadband loops are useful, in that they can be ground mounted and placed close to non-metallic items such as shrubs, trees and fences, and they can also be quite easily disguised domestic objects or garden furniture if you are not allowed any external antennas.
In my experience Wellbrook, LZ1AQ and Cross Country Wireless are among the best makes of commercial loops, others less so.
Regards,
Martin
Update to this issue:
Recently the noise floor went a bit higher, although nothing equipment-wise had been changed.
Problem traced to a LVPS feeding a set of LED lights on main floor in the kitchen. When shut off, noise issue cleared up entirely. I suspect this was a smaller problem before but somehow has become more noisy. The type, pattern and distribution of the interference as noted on the Kiwi is roughly the same, but the amplitude has increased.
So my next task I think, is to check into this supply and either repair (if I can) or replace. Doing these things around the usual issues of life, so things happen whenever there's a bit of time to get them done.
I also chatted with the neighbour having the solar array. He is managing partner of a very go od local heating/plumbing/electrical company. He had one of his electricians visit his house and apparently they found some connections which when cleaned up and re-tightened, solved the noise issue. So that's good (and likely helped his overall array efficiency too).
The other neighbours have been gone much of the summer and when they were here, didn't use their yard lights much. So that helped too ...
Martin, thanks for the thumbs-up on the LZ1AQ array. Before I purchased the kiwi I did a lot of Internet research as to what the best choice of antenna for this box was and this seemed to be the best "bang for the buck". As I mentioned earlier I'm pretty happy with this setup, it's very good with the kiwi, and works pretty well also with a couple of SDR RSP units.
consider yet an active noise canceller like MFJ-1026 or QRM eliminator ??
I have no relevant experience using them ..
Noise cancellers work by using two antennas and altering the amplitude and phase of the signal received by each antenna relative to each other.
This creates a directional antenna that allows you to 'steer' the antenna pattern to hopefully reduce or remove the interfering signal.
It takes a bit of time and practice to find the optimum settings as all the controls tend to interact with each other, and it can only work on one narrow band of frequencies and will generally only allow you to 'null' out one interference source at a time.
For these reasons it's really not much use with a wideband shared receiver such as the KiWi, but it can be useful for amateur radio operation, where only one operator is listing to only one frequency.
Some notes on noise cancellation can be found on my archived web pages.
https://web.archive.org/web/20230722120059/https://www.g8jnj.net/rfnoisecancellation.htm
Regards,
Martin
I see. Thanks a lot for the explanation. 😀
(... It can only work on one narrow band of frequencies and will generally only allow you to 'null' out one interference source at a time ）
It's not true that beam forming and noise cancellation can only work on a narrow band of frequencies.
By using a broadband antenna system such as the quadripole I show on my web pages along with a multi-decade quadrature network, also shown there, it is possible to create a system that has a controllable pattern over significant spectrum.
As an example, with the quadripole/polarimeter I am prototyping, I can achieve and maintain significant axial ratio to a polarization of more than one of the .06, 2.5, 5,10,15,25 MHz NIST WWV transmitters located about 20 km north of me.
Additionally it isn't necessary to maintain extreme values in every situation. 10-20 dB of nulling may be enough to make a very significant difference in SNR in many situations.
Hi Glenn,
The type I referred to are the low'ish' cost units available for the amateur market, and these tend to use narrowband tuned circuits or R/C networks in order to provide the required variable phase shift networks.
But I do agree with you, it is possible to achieve broadband beam steering, using hybrids to form a Butler Matrix.
https://en.wikipedia.org/wiki/Butler_matrix
This is common practice at major HF receive sites, so that the same antenna array can provide signals to large banks of receivers, with each feed having a different direction of lobe.
However, this is somewhat beyond the capabilities and costs that would be thought to be practical by a typical KiWi admin, myself included. Although I think I saw a home built one on a European amateur's QRZ page, but I can't find it to provide a link.
Perhaps the SDR Play RSP Duo is more like the sort of system envisaged earlier in the thread, using a pair of crossed loops.
https://www.sdrplay.com/video-demo-showing-diversity-software-for-noise-reduction/
Regards,
Martin